Electric power equipment, and especially transformers filled with dielectric liquid, operating in medium and/or high voltage networks, contain protective systems whose purpose is to eliminate the effects of various failures and to disconnect the power supply system from the network if an internal fault occurs in the transformer. The protective systems contain current-limiting fuses with tripping devices which control the disconnector and which are coupled with a control sensor used to control the pressure and level of oil inside the transformer tank. Exceeding the predetermined parameters of oil level or pressure results in shorting of fuses, and consequently in the disconnection of the transformer. In known solutions protecting transformers against internal faults, the disconnector whose movable contacts are situated on a rotary strip, contains current-limiting fuses, fixed to the rotary strip and suitably spaced in one row, the spacing resulting from the dimensions of the external insulators in which the current-limiting fuses are placed.
A device protecting against the effects of internal voltage surges in electrical equipment, and especially in a distribution transformer, is know from patent description EP 0817346. This devise is immersed in the dielectric liquid of the earthed tank of the transformer and it is connected with the structure of the active part of the transformer. The protective device contains a phase disconnection system and devices for detecting the flow of earth current between earth and the structure of the active part of equipment. The phase disconnection system which is provided with blocking devices with fixed contacts is attached to the rotary rod of the disconnector. In the closed position of the disconnector, the fixed contacts contact the tripping devices of the fuses. If one of the fuses blows, the freed tripping device, through a contact with a lever connected with the rod of the three-phase disconnector, causes a turn of the rod and the disconnection of the other fuses from the power supply system.
There are known TPC oil transformers, manufactured by Transfix Toulon, which contain a disconnector situated in the oil transformer tank and three or two medium voltage fuses, situated vertically in the tank. The fuses together with the tripping devices are situated in bushings which are fixed in one row to a rotary rod of a three- or two-phase disconnector which is situated in the bottom or upper part of the transformer tank. The disconnector is activated by the tripping device if a fuse blows. The use of vertical bushings with fuses arranged in a row in relation to the rotary rod of the disconnector causes that the disconnector occupies relatively much space inside the transformer tank.